MaxRaceSoftware

We've been on the dyno for a month with it and have made 741 at peak/ 712 avg. HP with it so far but we are trying to make around 755. It should still fly at 741 but you know how it is, never can have enough in Comp.
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<<<but you know how it is, never can have enough in Comp.>>

yes, i remember many years ago when Kenny 1st came to my Dyno and made
560 HP out of a BBC and was jumping up and down with excitement

just a month ago Kenny came with BBC that made 1263 HP
.....still wanting more

on that 1263 BBC engine, we had the 4/7 swap
it seemed to make 20 HP gain at 600 Rpm/Sec

but i can't be entirely sure , i try to Post data that i know i've controlled all the variables myself and not rely on what customer telling me he did
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Thanks for Posting some great data on 4/7 swap !!
hard to nail down sometimes.

DR.ZED

Well done and two thumbs up for the real-world info here.

Thanks gents.

Damon

Allen Sherman- Agreed that 5 & 7 "steal" from eachother in a traditional firing order but in the "altered" 4/7 cam you then have 4 & 2 at the front of the motor on the other bank "stealing" from eachother in exactly the same way. No?

Seems to me there's only so much you can do, short of going to a 180* crankshaft. You then get TRUE even bank-to-bank pulsing to help out not only the intake but probably even more importantly, exhaust scavenging in the exhaust collectors.

MaxRaceSoftware

Example=> Big Block Chevy
with heads such as Edelbrock Victor Race alum BBC
with (2) Holley 0-9375 carbs

Good Port Direction=Cylinders=> 1,5,8,4
Higher Mid-to-High Lift Flow
Higher Mid-to-High Lift Flow Rates
Longer Mid-Port Lengths
Larger Runner CC's

Bad Port Direction=Cylinders=>3,7,6,2
Lesser Mid-to-High Lift Flow
Lesser Mid-to-High Flow Rates
Shorter Mid-Port Lengths
Smaller Runner CC's

Normal Firing Order= 1-8-4-3-6-5-7-2

Normal Firing Order=> (2)-4-Barrell Signals=> F-R-F-F-R-R-R-F reverting back to F...so there are (3) successive (R) rear carb signals..along with B-G-B Ports

Normal Firing Order=> relative to Cyl Head Ports=>
G-G-G-B-B-G-B-B ..then reverting back to G
so there are (3) successive (G) Good Port Intakes
===========================================

4/7 Swap => 1-8-7-3-6-5-4-2

4/7 Swap (2) 4-Barrell Signals => F-R-R-F-R-R-F-F ..reverting back to F so there are (3) successive (F) front carb signals..along with G-B-G ports

and;
4/7 Swap relative to Cyl Head Ports=>
G-G-B-B-B-G-G-B..then reverting back to G
so there are (3) successive (B) Bad Port Intakes

Whats this all mean ? =>
with the above type Cylinder Head, Tunnel-Ram Intake, with (2)-4 Barrell carbs

the 4/7 Swap will have better mixture distribution,

smaller mixture distribution flow triangle,

cause the intake to "think" the Plenum area is larger

cause the plenum area to "dampen" reversion pulses better

cause the carbs to "act" like they are larger

cause the engine to have a more uniform mixture distribution
under GForce acceleration because 2 & 4 are paired and firings are 6-5-4-2 middle-to-front pattern

increase the capability to make more HP at higher RPMs or extend the RPM curve past Peak Hp Point

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the Normal Firing Order will cause a "larger" mixture flow triangle
producing lesser mixture distribution

under GForce acceleration 5 & 7 are paired causing more mixture to rear, then Firings are 6-5-7-2 =>middle-rear-front pattern
producing less mixture distribution

cause the plenum area to "dampen" LESS

cause the carbs to act SMALLER

decrease the ability of engine to make more Peak HP and more HP after the Peak HP point

==========================================

the Exhaust pulses and wave tuning shouldn't matter with Normal Firing Order -VS- 4/7 Swap

==============================================

This is just one Big Block Chevy Example

can be completely different with another Cylinder Head Port layout design

and again different effects with SBC heads and other brand engines

then there are added crankshaft torsional effects to account for
that can make HP/Torque differences..just the same sort of effects when trying different Harmonic Dampner Balancers
in Dyno accel tests....from 4/7 swap -VS- Normal

sleepybu

after reading the last 4+ pages it would apear the a 4/7 swap wouldn't make any difference on a boosted motor???

or is that a hole different story

MaxRaceSoftware

after reading the last 4+ pages it would apear the a 4/7 swap wouldn't make any difference on a boosted motor???

or is that a hole different story

==============================

my previous Post was just a few "Probabilities" of what could be happening with a 4/7 swap in a BBC w/conventional type head

with a Blower 's rotors mixing up mixture ...or with fuel injection, nitrous ,....could be entirely different results

and only 3 possibilities
1-gain hp/tq
2-loose hp/tq
3-no difference in hp/tq

sleepybu

someone has to try it

squinn

Its seem alot of people have seen gains on carb motors with the 4/7 swap, maybe the gain is seen because it makes the motor think it has a bigger carb. What would happen if you put a bigger carb on that same motor would you still see the same gain? Has anyone done any testing with an efi setup and seen a gain? I've been told that with an efi setup you will not have a gain, as you can use the fuel trim to do the same thing. My feeling on that is, if you have to use the fuel trim something is wrong in you intake system. What is the point of having a cnc head and blue printed short block where ever thing is the same, it should require the same fuel on ever cylinder to make the same power on ever cylinder.

MaxRaceSoftware

squinn.....checkout Hot Rod mag article on the fastest LS-1 and LS-6 Cars in US

Alan Futral MotorSports had the fastest 6 speed (346 cid)

Alan just dropped off a couple pairs of heads for me to Port

forgot to ask Him if he tried the conventional -VS- 4/7 swap with any of EFI engines/cars hes working on

i'll ask Alan tomorrow about chassis dyno and dragstrip results
he might have seen with EFI and 4/7 swap and later Post this info

jimlab

Just FYI, I talked with tech at Comp Cams last week and was told that a 4/7 swap would require an SBC core that would not work with the LT1 roller cam retainer plate and would require a cam button/SBC-style front cover setup. I was also told that such a cam would cost roughly $1,000. I don't believe this was just a blow-off, because he actually did a lengthy search for a core that would work for what I was asking for.

I ended up going with what he recommended; 242/248 @ 0.050", 0.610"/0.616" (1.6:1), 112 lsa, on an "08" core ("TPI" solid roller, no Opti drive pin needed for FAST eDist setup). Price was about $310.

Nitromethane

I have a cam sitting here with the 4/7 swap from cam motion, haven't installed it yet but I am tempted to order another cam sometime later this year, identical spec but no 4/7 swap to do a comparison.

jimlab

What did you pay for the Cam Motion 4/7 cam? Once I have my cam (and cam card), I may give them a call and see if they can duplicate my specs but with a 4/7 swap if the price isn't too high.

squinn

Cam Motion told me the price was $475 for and LT1 4/7 cam, and 5 to 8 weeks as they have to start from scratch to do a LT1 4/7 cam. As on on std SBC they have cores to do them 4/7.

SAR2K

I'm in the process of a new build right now and actually thought about doing this. After reading this thread I'm going to give it a shot.
Steve...

jimlab

Cam Motion just recommended a 253/258 @ 0.050", 0.664"/0.656" 112 lsa grind through their cam request form.